Presently, many providers of telephony service offer subscribers the ability to pay in advance. A subscriber seeking pre-paid telephony service first enrolls with a telephony service provider by depositing a certain sum of money. The service provider then credits this amount to a pre-paid service account identified by a Personal Identification Number (PIN) unique to the subscriber. Many providers of pre-paid telephony service have greatly simplified the enrollment process by offering pre-paid cards that have a particular currency denomination corresponding to a certain amount of service (i.e., a prescribed number of minutes). The card itself carries the PIN identifying the corresponding pre-paid account maintained by the telephony service provider for pre-paid service. Additionally, the card carries an access telephone number that the subscriber dials to reach a pre-paid service platform in the telephone service provider's network.
To obtain pre-paid telephony service, the subscriber dials the access number, whereupon the telephony service provider prompts the subscriber for the PIN. The service provider then undertakes verification of the PIN as well as validation of the account to ensure that a sufficient credit balance exists. Upon successful verification of the PIN and validation of the account, the telephony service provider prompts the subscriber for the telephone number of the called party. Once the subscriber enters the number, the telephony service sets up the call to the called party, and during the course of the call, the service provider debits the pre-paid account by the cost of each incremental call unit (e.g., each minute of the call.) Should the account balance fall below the cost of the next incremental call unit, the telephony service provider will terminate the call, or alternatively, offer the subscriber the opportunity to replenish the pre-paid account balance.
Pre-paid telephony service currently enjoys tremendous popularity, due in part to the relative security afforded to subscribers by the Public Switched Telephone Network. Generally, little risk exists that an unauthorized person can intercept the PIN entered by the subscriber in connection with a pre-paid call made from a wired telephone set. However, the risk increases substantially when the subscriber utilizes an analog cordless telephone to place the pre-paid call since such cordless telephones radiate an RF signal that is easily intercepted.
The problem of potential interception of personal identification data transmitted across a wireless link also exists in connection with other types of prepaid telecommunications service. Currently, some service providers offer fee-based wireless LAN access that allow users to gain access through the LAN to a private data network or a public data network such as the Internet. Such wireless LANS have begun to emerge at various publicly accessible facilities, such as rest stops, cafes, and libraries for example. Upon entering such a publicly accessible facility, the user establishes a communication link with an access point, usually over a wireless channel to gain access to the LAN, and a public or private network therebeyond. When initiating a communications session with the wireless LAN, the user needs to provide a PIN that identifies the pre-paid account or a credit card account number to provide payment for access fees. Often, the transmission of the PIN occurs without any encryption because the user is accessing the wireless LAN for the first time. Thus, in the absence of any prior relationship with the subscriber, the LAN lacks any key by which to decrypt an encrypted subscriber transmission. An unencrypted transmission of sensitive information such as a PIN creates a serious security risk since hackers can often readily intercept wireless LAN traffic.
Thus, there is need for a technique for that enables secure authentication of a wireless LAN user.